Paper machine lubricating oil distribution systems and their problems are described in the Finnish publication print 65661 and the related opposition documents. It is usual for there to be about 300 lubricated bearings in an older paper machine. In newer machines, there may be 600-700 such bearings. Besides lubricating the bearings, the oil cools them, making it important that the correct amount of oil goes to each bearing, and also making it necessary to monitor the oil flow to each bearing separately. For monitoring purposes, the oil is distributed to the bearings by means of a centralized system through a distribution and measuring unit consisting of 5-20 meters. Typical types of meters are visually read rotameters and volumetric flowmeters. The latter include elliptical wheel, turbine, and jet meters, which provide a commensurate indication of the flow.
In the above-mentioned publication, the installation of several volumetric meters in the same unit is shown to have a branch pipe belonging to a common unit. The measurements from the meters are transmitted as electrical impulses to a place that is advantageous from the point of view of control.
The known meter units are inflexible because all are of the same kind. However, many paper machines manufacturers and users would like some of the meters to be flowmeters and some volumetric meters. It is also difficult to change the meters later. However, it is only after a paper machine has been operated for some time that the correct specifications for a meter can be ascertained. There may also be various reasons to change the meters in a paper machine that is already in operation. In known systems, it is not possible to install meters or other components during operation, instead one must wait for the next maintenance shutdown.
Despite meters being collected in units of the present type, complicated pipework is nevertheless required during installation. The directions of the input and output pipes of the unit are always determined beforehand so that in variable cases the pipes must be turned according to each case. Because of its thickness, the incoming feed pipe cannot be bent, which means that pipe bands must be welded onto it.